1. Field of the Invention
The present invention relates to a vehicle headlamp and, more particularly, to a bulb attaching structure of the vehicle headlamp.
2. Description of the Related Art
According to a related art bulb attaching structure of a vehicle headlamp, an insertion hole is formed through a reflector of a lamp unit to insert a light emitting portion of a bulb, and behind the insertion hole, an attaching portion is provided to attach a connector housing to which terminals protruding from a rear face of the bulb are fitted and connected. The terminals on the rear side of the bulb are inserted and connected to the connector housing, and the light emitting portion of the bulb is then inserted into the insertion hole of the reflector from a back side. As a flange of the bulb is pushed against a hole edge portion on a back face of the reflector around the insertion hole, the connector housing is attached to the attaching portion, whereby the bulb is securely attached to the reflector (see, e.g., JP 2002-373509 A).
In headlamps of this type, when a bulb is blown out, or in order to improve performances such as luminance of light emission, it is not infrequent that the bulb is replaced with another bulb, and it is possible that a bulb of a different manufacturer is selected.
While dimensions and the like of the bulbs are standardized to a certain extent, standardization level of a connecting portion of the bulb, including the terminals, is relatively low, which means that a tolerance range is relatively wide. In fact, there are differences among the manufacturers with respect to a protruding length and an arrangement of a terminal of a bulb, a configuration of a portion of a flange of the bulb that is brought into contact with a hole edge portion around an insertion hole, a dimension from the flange to a bottom face of the connecting portion from which the terminal protrudes, etc.
Under such circumstances, when there is a difference in a protruding length of the terminal and/or a dimension from the flange to the bottom face of a connecting portion upon replacement of the bulb, in a state in which the new bulb is inserted into the insertion hole of the reflector to place the flange onto the hole edge portion, the connector housing may not reach its attaching portion, or even if the connector housing is attached to the attaching portion, the connecting portion of the bulb may move, i.e. play between the back face of the reflector and the connector housing.
Further, while three positioning tabs are provided to protrude from an outer circumference of the flange of the bulb and to engage with respective positioning recess portions on the back face side of the reflector so that a rotational position of the attached bulb is fixed, when there is a difference in a positional relationship between a the positioning tabs and the terminals with respect to a circumferential direction upon replacement, the connector housing connected to the bulb is shifted around its axis from a proper orientation, in which case the connector housing cannot be attached.
In some cases, furthermore, depending on the configuration of the portion of the flange that contacts the hole edge portion of the insertion hole, the bulb may have to be attached with its axis being tilted, which causes a number of problems. For example, because the axis of the housing connector that is connected to the bulb also tilts, the connector housing cannot be attached.